Why Am I Friends With These People?

So, I was hanging out after school, having received my exam results, so decided to discuss my results with my friends. We were mid-way through talking about how Geography was a horrible subject and how it should die in a fire when another of my friends came up. He is usually the only bastion of sanity in the entirety of Year 8, but today, he seemed to have gone mad.

Crazy Friend: I think I drank [Friend Whose Name Starts With 'I']'s blood.

Me: ...

Other Friend: ... What?

Crazy Friend: I think I need to drink some water.

*He goes off to drink water from the nearby tap, and soon returns.*

Me: So ...

Crazy Friend: Hm?

*I turned to look around, and end up seeing the 'Friend Whose Name Starts With 'I' walking down the stairs, so I call out to him.*

Me: Hey! Did [Crazy Friend] drink your blood!?

FWNSWI: Yes!

*I turn back to my Crazy Friend.*

Me: Dude, that's creepy.

Crazy Friend: *Shrugs* It isn't that bad. I mean, drinking his blood might be good for me. FWNSWI is a player.